1. Field of the Invention
The present invention relates to a light emitting diode, and more particularly, to a light emitting diode (LED), wherein a structure that is capable of reducing total reflection of light is formed within or on the surface of a semiconductor layer on a top or bottom surface of an active layer so that light from an LED is efficiently extracted to enhance luminance.
2. Description of the Related Art
The technology for fabricating light emitting diodes (LEDs) using Group III/V semiconductor materials has expanded its application range from the development of red LEDs using AlGaAs/GaAs into the development of red and green LEDs using AlGaInP/InP. Recently, full colors can be implemented due to the development of blue LEDs using GaN-based materials, so that the use of LEDs has widely expanded into signal lamps, full-color displays and the like.
Further, GaN-based materials have been connected to the development of ultraviolet LEDs, thereby more increasing the possibility of LEDs for general use in lighting apparatus in the future.
Although such various kinds of LEDs have been developed and widely used, studies on enhancing luminance of LEDs still have been conducted.
To enhance luminance of LEDs, there have been conducted studies on methods of improving structures in growth of the LEDs, and improving chip designs and assemblability.
However, if quantum efficiency is taken into consideration, there are limitations on methods of enhancing luminance by modifying structures of LEDs. Thus, studies on enhancing extraction efficiency to improve extraction of light generated inside LEDs have actively been conducted in recent years.
To enhance such extraction efficiency, there have been made various attempts to decrease absorption or reflection of the light generated at an interface between materials. For example, to reduce total reflection generated at an interface between sapphire and a nitride in a nitride-based LED, a method of forming patterns or corrugations on a sapphire substrate has been mainly used, and a method of eliminating absorption or total reflection by separating a sapphire substrate has also been attempted.
Further, to reduce total reflection caused by a difference in refractive indexes of a nitride and air, there is a method of enhancing extraction efficiency by roughening a surface of the nitride.
Moreover, there have been attempted many methods of efficiently extracting light generated inside LEDs by improving chip designs and assemblability.